1. Field
This disclosure relates to a light-emitting material including a polysilsesquioxane having a ladder structure, specifically a polysilsesquioxane having a ladder structure with photoactive groups bonded at the siloxane backbone, a thin film prepared therefrom, and an organic electronic device including the same.
2. Description of the Related Art
In general, a hybrid material consisting of organic and inorganic components may exhibit significantly improved thermal, mechanical and chemical properties over the two components. Particularly, polysilsesquioxane (PSQ) with the empirical formula (RSiO1.5)n allows introduction of various functional groups via a relatively easy method and, due to superior cotability, is used as a thin film material in various fields.
In addition, the functional groups covalently bonded to the siloxane structure often show superior performance which is hardly found in organic based polymers. For example, a polyhedral oligomeric silsesquioxane (POSS) of the following formula having photoactive groups exhibits a significantly improved photoluminescence efficiency over similar organic based polymers.
These are related with the aggregation of functional groups in existing organic polymers. Since most of organic polymers have their functional groups bonded to short, flexible carbon chains, the functional groups tend to aggregate and do not exert desired luminescence efficiencies.
In contrast, since the siloxane bonding provides a rigid backbone, it prevents the functional groups attached to the side chains from aggregating and allows the functional groups to move freely as if in liquid phase. For these reasons, development in organic-inorganic hybridization has been made a lot with respect to the POSS having stable and continuous siloxane bondings.

However, despite the various interesting phenomena of POSS, it does not make a practical material for use as a thin film in electronic devices such as organic light-emitting diodes (OLED) or organic photovoltaic cells because of low molecular weight, which results in relatively low glass transition temperature and melting point.